Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to high security (anti-theft) constructions for fasteners, and particularly locking wheel nuts and wheel bolts used to secure vehicular wheels.
2. Description of the Prior Art
By way of background, locking wheel nuts and wheel bolts are commonly used to attach wheels to axle hub assemblies of automobiles and other vehicles. These fasteners are designed with security features that are intended to thwart theft by rendering the fasteners difficult to remove with conventional tools. In particular, the fasteners do not have the usual hexagonal head pattern found on conventional nuts and bolts, and instead have smooth cylindrical side walls that cannot be gripped by standard wrenches. Fastener removal requires the use of a special security tool having a unique key pattern that matches a corresponding groove pattern formed in the fastener end face.
Additional security can be obtained by fitting a free-spinning shroud over the security fastener""s cylindrical side walls, such that the shroud is in concentric relationship therewith. The shroud discourages the use of theft devices that could otherwise be used to grip the side walls and remove the fastener without an authorized security tool. Because the shroud substantially surrounds all exposed surfaces of the side walls, no rotational purchase can be obtained on the fastener. The theft device can only engage the shroud, which freely spins under action of the theft device while the main body of the fastener remains stationary.
Commonly assigned U.S. Pat. Nos. 4,618,299, 4,726,723, 4,897,008, 5,112,176, 5,360,304, and 5,730,567 are directed to shrouded fastener designs of the foregoing type. The patented designs feature shrouds of various shape and size for both locking wheel nuts and wheel bolts. It is to such security fasteners that the present invention is directed. In particular, the present invention offers alternative security fastener constructions in which security shrouds are combined with locking wheel nuts and wheel bolts in a manner that minimizes design complexity and manufacturing expense while maintaining the requisite anti-theft characteristics.
The foregoing goals are achieved and an advance in the art is provided by a series of high security fastener constructions featuring rotatable anti-theft shrouds mounted on locking wheel nuts and wheel bolts designed for vehicular wheels. Each construction features (1) a fastener body having a first body end adapted to accommodate a key receiving pattern or member, a second body end having a thread pattern extending therefrom, and a shroud receiving portion located between the first and second body ends, (2) a shroud concentrically mounted on the shroud receiving portion, and (3) a shroud retaining system retaining the shroud for rotation relative to the fastener body such that the shroud will rotate under an applied torque prior to the fastener rotating when it is installed at a design installation torque.
In a first exemplary fastener construction, the shroud retaining system includes a shroud securement structure formed on the fastener""s shroud receiving portion. The shroud securement structure is adapted to axially secure the shroud on the body via radial engagement therewith. In particular, the shroud securement structure has a radial face configured to radially engage the shroud in interfering relationship to form a radial interference connection. The radial interference connection provides an engagement torque that is less than a design installation torque of the fastener. Thus, when the fastener is secured in engagement with an external structure at the design installation torque, the shroud will rotate before the fastener rotates.
In a second exemplary fastener construction, the shroud retaining system includes first and second shroud retaining members respectively disposed in facing relationship with first and second annular faces of the shroud. The first shroud retaining member is preferably integrally formed as part of the fastener body. The second shroud retaining member is implemented as a discrete seat member having a suitably shaped exterior face that provides a mounting seat for the fastener.
In a third exemplary fastener construction, the shroud retaining system includes a staking region formed on the fastener""s shroud receiving portion to allow staking of the shroud to the fastener body. The shroud is staked at the staking region to retain the shroud in rotatable relationship with the fastener body.
In a fourth exemplary fastener construction, the shroud retaining system includes first and second shroud retaining members respectively disposed in facing relationship with first and second annular faces of the shroud. The first shroud retaining member is preferably integrally formed as part of the fastener body. The second shroud retaining member is formed as a retaining ring retained on the fastener body.
In a fifth exemplary fastener construction, the shroud retaining system includes first and second shroud retaining members respectively disposed in facing relationship with first and second annular faces of the shroud. The first shroud retaining member is a discrete key receiving member mounted on the fastener body and having a key receiving pattern formed therein. The second shroud retaining member is preferably integrally formed as part of the fastener body.
In each of the foregoing fastener constructions, the shroud can be formed as a substantially tubular member in order to simplify the fastener""s construction and reduce manufacturing costs. Shrouds of other shape are not necessarily precluded, however, and it should be understood that a variety of shroud configurations may be used in the various fastener constructions of the invention.